This invention relates to maintaining frame synchronization between the receiver and the transmitter in a trellis-coded communication system.
In some trellis-coded communication systems the two-dimensional signal points sent by the transmitter are grouped into frames, and the receiver must be able to identify (i.e. synchronize itself to) the beginning of each frame for proper operation.
In so-called multi-dimensional trellis-coded systems (for example systems of the kind disclosed in Wei, U.S. patent application Ser. No. 727,398, filed Apr. 25, 1985, assigned to the same assignee as this invention, and incorporated herein by reference) the two-dimensional signal points carried on the channel between the transmitter and receiver are organized as multi-dimensional signal points, each multi-dimensional signal point comprising more than one two-dimensional signal point. At the receiver, in order to decode the multi-dimensional signal points, the receiver must be synchronized to identify the first two-dimensional signal point of each multi-dimensional signal point.
In so-called multiplexed communication systems, a high-bit-rate stream of bits to be transmitted is segmented into multiplexing frames. Each frame is built up (multiplexed) based on bits delivered from several ports each serving a relatively low-bit-rate data source. Each frame is transmitted as a group of signal points. At the receiver, in order to demultiplex each such multiplexing frame for delivery to several corresponding ports serving relatively low-bit-rate data sinks, the receiver must be able to locate the beginning of each group of signal points.